1. Field of the Invention
The present invention relates to generally to support arms forming part of an articulated stand for supporting a load, and particularly to a swivel arm for transmitting torque between a pair of rotating shafts in a stand, for example a surgical microscope stand.
2. Description of the Related Art
More and more surgical microscopes are used in surgery. Because of their high intrinsic weight, they must be supported by stands. Several well-known manufacturers have put stands on the market, and from a mechanical and static perspective they correspond well to the load-carrying requirements of the surgical microscope. For example, the assignee of the present application markets stands with the designation OH, which were manufactured by Mitaka. An example of such a stand can be found in European Patent Publication No. 628290. A further development of this stand is described in commonly owned PCT International Publication No. WO 97/13997.
Most of the more recent stands utilize parallelogram support arms to bear the weight of the surgical microscopes over the greatest possible distances without bending or distortion, so that the freedom of movement and the operating radius of the microscopes are as large as possible. For example, the aforementioned EP-A-628290 presents such a construction. The stand of EP-A-628290 also provides a parallelogram "swivel arm" for the swiveling support of a surgical microscope directly attached thereto. The purpose of the parallelogram support arms is to conduct retention forces for the load, i.e. for the surgical microscope, to the stand so that the microscope remains stable in its position when brakes on the stand are locked. There is a need for two adjustable carriage guides for the two upper parallel supports of a conventional parallel guide bar arrangement.